(1) Field of the Invention
The present invention relates to a fiber-reinforced polymeric resin composite material and a process for producing same. More particularly, the present invention relates to a fiber-reinforced polymeric resin composite material useful as a reinforcing material for shaped or molded polymeric resin materials, particularly for shaped or molded polymeric resin materials for civil engineering and construction, and a process for producing same.
(2) Description of the Related Arts
In the prior art, it is known that a thermoplastic polymeric resin material reinforced by a fiber material is produced by a process comprising the steps of knead-mixing a melt of a thermoplastic polymeric resin with chopped strands prepared by cutting a reinforcing fiber bundle into a length of about 5 mm in an extruder; extruding the mixture through the extruder; cutting the extruded strands to provide pellets; and converting the pellets to a shaped or molded article.
This conventional process has the following disadvantages:
(1) Where the reinforcing fiber bundle is composed of organic fibers, for example, wholly aromatic polyamide (aramide) fibers, the resultant chopped strands form a bulky mass, and thus it is difficult to smoothly feed the bulky chopped strands into an extruder or kneader.
(2) Where the reinforcing fiber bundle is composed of inorganic fibers, for example, carbon fibers or glass fibers, and the resultant chopped fibers are knead-mixed with a polymeric resin melt in an extruder or kneader while a high shearing force is applied thereto, the fibers are easily broken and converted to small particles having a size of about 5 mm or less. The resultant inorganic small particles exhibit substantially no or a very poor effect of reinforcing the shaped or molded polymeric resin article.
Also, it is known that, when recently developed heat-resistant resin materials, for example polyphenylene sulfide (PPS), polyetherether ketone (PEEK) or polyether sulfone (PES), reinforced by a fiber bundle, are subjected to a pellet-forming process in an extruder or to a injection-molding process, a bundling agent applied to the reinforcing fiber bundle is thermally degraded, and thus the dispersion of the individual fibers in the resin matrix becomes difficult.
Further, it is known that, when a fiber bundle-reinforced polymeric resin article is employed at a high temperature, water vapor is generated from the fiber bundle and a bundling agent applied to the fiber bundle is thermally decomposed or modified so as to generate water vapor or another decomposition gas, and thus the heat resistance and mechanical strength of the fiber bundle-reinforced polymeric resin article are lowered by the generation of water vapor or other decomposition gas.
Japanese Unexamined Patent Publication Nos. 62-240351 and 57-90020 disclose means for eliminating the above-mentioned disadvantages, but these means are effective only for eliminating the difficulty in the feeding of the bulky chopped strands to the extruder or kneader or for preventing the breakage of the chopped strands in the extruder or kneader, and the disadvantages derived from the generation of water vapor and the decomposition gas are not eliminated by the above-mentioned prior arts.
It is important that individual fibers in the fiber bundle-reinforced polymeric resin article be covered by the polymeric resin, but, in the conventional fiber bundle-reinforced polymeric resin article produced by impregnating a fiber bundle with a polymeric resin melt having a high viscosity under the ambient atmospheric pressure, only the outside periphery of the fiber bundle is covered by the polymeric resin, and the peripheries of individual fibers in the fiber bundle are not completely covered by the polymeric resin. Therefore, in the conventional fiber bundle-reinforced polymeric resin article, the reinforcing effect of the individual fibers is not satisfactory.
Japanese unexamined Patent Publication No. 61-40113 discloses a fiber-reinforced polymeric resin article in which reinforcing continuous multifilaments are dispersed in a matrix consisting of a polymeric resin without preheating the multifilaments at a temperature not lower than the melting point of the polymeric resin. In this article, the individual multifilaments are substantially completely covered by the polymeric resin, but the bundling agent applied to the multifilaments is still maintained on the multifilaments and generates a decomposition gas at a high temperature. Therefore, the resultant shaped or molded article exhibits a lower heat resistance and mechanical strength.
Furthermore, it is important that the continuous multifilaments be uniformly dispersed and mixed in the polymeric resin matrix in the longitudinal direction of the multifilaments, but the process as disclosed in the above-mentioned Japanese Publication does not provide a satisfactory even dispersion of the multifilaments in the polymeric resin matrix.